In recent years, in order to address air pollution and global warming, it has been eagerly desired to reduce the amounts of carbon dioxide emitted. In the automotive field, the anticipation is that, by introducing electric vehicles and hybrid electric vehicles and so on, it will be possible to reduce the amounts of carbon dioxide emitted. And the development of cells for driving electric motors is a key to practical implementation of such vehicles, and is being energetically performed.
Attention is being directed to a lithium ion secondary cell as a cell for driving an electric motor, since they have high theoretical energy, and currently their development is progressing rapidly to achieve a cell with higher performance. Generally, a lithium ion secondary cell includes a positive electrode, a negative electrode and an electrolyte disposed between these, all housed in a cell casing. The positive electrode is formed by applying a positive electrode slurry including a positive electrode active material upon surface of a current collector, and the negative electrode is formed by applying a negative electrode slurry including a negative electrode active material upon surface of a current collector.
In the prior art, an electrode structure, in which the adhesion between a surface of a current collector and an active material layer provided on a current collector is improved, has been proposed. In this electrode structure, an electrically conductive resin layer is formed upon at least one side of an electrically conductive substrate, the surface roughness Ra of this electrically conductive resin layer is 0.1 μm or greater and 1.0 μm or less, a current collector that is employed is in a range satisfying (⅓)t+0.5≤θa≤(⅓)t+10, when the layer thickness of this electrically conductive resin layer is termed t [μm] and the average inclination angle of the recesses and projections on the surface of the resin layer is termed θa [°], and an active material layer formed upon this electrically conductive resin layer is employed (Please refer to International Publication No. 2013/018686.).